The normal electrical conduction of the heart allows electrical propagation to stimulate the myocardium. Time ordered stimulation of the myocardium allows efficient contraction of all four chambers of the heart, thereby allowing selective blood flow through both the lungs and systemic circulation. The ordered stimulation can become de-synchronized and thereby adversely affect the mechanical function of the heart.
Cardiac resynchronization therapy (CRT) is a method of improving the mechanical function of the heart using electrical therapy (e.g., pacing both the right and left ventricles). Various techniques are utilized to determine a pacing site as well as to determine pacing parameters. Current mechanical and electrical measures tend to be qualitative and are highly operator dependent due to the complex nature of ventricular activation and the lack of quantitative comparisons between electrical activation and mechanical function.